diff --git a/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java b/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
index be852ce..2f177bd 100644
--- a/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/query/TestKorapQueryJSON.java
@@ -265,7 +265,6 @@
 	assertEquals(sqwi.toQuery().toString(), "shrink(1: spanEndsWith(<tokens:s />, {1: tokens:mate/p:V}))");
     };
 
-
     @Test
     public void queryJSONrepetition () throws QueryException {
 	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/bsp-repetition.jsonld").getFile());
@@ -283,6 +282,10 @@
     };
 
 
+    /*
+      Check extensions
+     */
+
     @Test
     public void queryJSONseqEmpty () throws QueryException {
 	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty.jsonld").getFile());
@@ -353,6 +356,50 @@
 	assertEquals(sqwi.toQuery().toString(), "spanNext(tokens:s:der, spanExpansion(tokens:tt/p:NN, []{4, 8}, left))");
     };
 
+    @Test
+    public void queryJSONseqEmptySurround () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround.jsonld").getFile());
+	// [][tt/p=NN][]
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{1, 1}, left), []{1, 1}, right)");
+    };
+
+    @Test
+    public void queryJSONseqEmptySurroundClass () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround-class.jsonld").getFile());
+	// [][tt/p=NN]{2:[]}
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{1, 1}, left), []{1, 1}, right, class:2)");
+    };
+
+    @Test
+    public void queryJSONseqEmptySurroundClass2 () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround-class-2.jsonld").getFile());
+	// {3:[]}[tt/p=NN]{2:[]}
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{1, 1}, left, class:3), []{1, 1}, right, class:2)");
+    };
+
+    @Test
+    public void queryJSONseqEmptySurroundRepetition () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround-repetition.jsonld").getFile());
+	// [][tt/p=NN][]{2,7}
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{1, 1}, left), []{2, 7}, right)");
+    };
+
+    @Test
+    public void queryJSONseqEmptySurroundRepetition2 () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround-repetition-2.jsonld").getFile());
+	// []{3,5}[tt/p=NN][]{2,7}
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{3, 5}, left), []{2, 7}, right)");
+    };
+
+    @Test
+    public void queryJSONseqEmptySurroundRepetitionClass () throws QueryException {
+	SpanQueryWrapper sqwi = jsonQuery(getClass().getResource("/queries/sequence/empty-surround-repetition-class.jsonld").getFile());
+	// {1:[]}{3,8}[tt/p=NN]{2:[]{2,7}}
+	// Ist gleichbedeutend mit
+	// {1:[]{3,8}}[tt/p=NN]{2:[]}{2,7}
+	assertEquals(sqwi.toQuery().toString(), "spanExpansion(spanExpansion(tokens:tt/p:NN, []{3, 8}, left, class:1), []{2, 7}, right, class:2)");
+    };
+
     public static String getString (String path) {
 	StringBuilder contentBuilder = new StringBuilder();
 	try {
diff --git a/src/test/resources/queries/sequence/empty-surround-class-2.jsonld b/src/test/resources/queries/sequence/empty-surround-class-2.jsonld
new file mode 100644
index 0000000..5f15478
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround-class-2.jsonld
@@ -0,0 +1,37 @@
+{
+   "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+   "query" : {
+      "@type" : "korap:group",
+      "operands" : [
+	 {
+	     "@type" : "korap:group",
+	     "class" : 3,
+	     "operation" : "operation:class",
+	     "operands" : [
+	     	 {
+             "@type" : "korap:token"
+}]
+         },
+         {
+            "@type" : "korap:token",
+            "wrap" : {
+               "@type" : "korap:term",
+               "foundry" : "tt",
+               "key" : "NN",
+               "layer" : "p",
+               "match" : "match:eq"
+            }
+         },
+	 {
+	     "@type" : "korap:group",
+	     "class" : 2,
+	     "operation" : "operation:class",
+	     "operands" : [
+	     	 {
+             "@type" : "korap:token"
+	     }]
+         }
+      ],
+      "operation" : "operation:sequence"
+   }
+}
\ No newline at end of file
diff --git a/src/test/resources/queries/sequence/empty-surround-class.jsonld b/src/test/resources/queries/sequence/empty-surround-class.jsonld
new file mode 100644
index 0000000..2c5846f
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround-class.jsonld
@@ -0,0 +1,31 @@
+{
+   "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+   "query" : {
+      "@type" : "korap:group",
+      "operands" : [
+	 {
+             "@type" : "korap:token"
+         },
+         {
+            "@type" : "korap:token",
+            "wrap" : {
+               "@type" : "korap:term",
+               "foundry" : "tt",
+               "key" : "NN",
+               "layer" : "p",
+               "match" : "match:eq"
+            }
+         },
+	 {
+	     "@type" : "korap:group",
+	     "class" : 2,
+	     "operation" : "operation:class",
+	     "operands" : [
+	     	 {
+             "@type" : "korap:token"
+	     }]
+         }
+      ],
+      "operation" : "operation:sequence"
+   }
+}
\ No newline at end of file
diff --git a/src/test/resources/queries/sequence/empty-surround-repetition-2.jsonld b/src/test/resources/queries/sequence/empty-surround-repetition-2.jsonld
new file mode 100644
index 0000000..789fc53
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround-repetition-2.jsonld
@@ -0,0 +1,46 @@
+{
+   "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+   "query" : {
+      "@type" : "korap:group",
+      "operands" : [
+	 {
+	 "@type" : "korap:group",
+	 "operation" : "operation:repetition",
+	 "boundary": {
+	   "@type" : "korap:boundary",
+	   "min" : 3,
+	   "max" : 5
+	 },
+	 "operands" : [
+	   {
+             "@type" : "korap:token"
+}]	     
+         },
+         {
+            "@type" : "korap:token",
+            "wrap" : {
+               "@type" : "korap:term",
+               "foundry" : "tt",
+               "key" : "NN",
+               "layer" : "p",
+               "match" : "match:eq"
+            }
+         },
+	 {
+	 "@type" : "korap:group",
+	 "operation" : "operation:repetition",
+	 "boundary": {
+	   "@type" : "korap:boundary",
+	   "min" : 2,
+	   "max" : 7
+	 },
+	 "operands" : [
+	   {
+
+             "@type" : "korap:token"
+}]	     
+         }
+      ],
+      "operation" : "operation:sequence"
+   }
+}
\ No newline at end of file
diff --git a/src/test/resources/queries/sequence/empty-surround-repetition-class.jsonld b/src/test/resources/queries/sequence/empty-surround-repetition-class.jsonld
new file mode 100644
index 0000000..8a584dc
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround-repetition-class.jsonld
@@ -0,0 +1,61 @@
+{
+  "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+  "query" : {
+    "@type" : "korap:group",
+    "operands" : [
+      {
+	"@type" : "korap:group",
+	"operation" : "operation:repetition",
+	"boundary": {
+	  "@type" : "korap:boundary",
+	  "min" : 3,
+	  "max" : 8
+	},
+	"operands" : [
+	  {
+	    "@type" : "korap:group",
+	    "class" : 1,
+	    "operation" : "operation:class",
+	    "operands" : [
+	      {
+		"@type" : "korap:token"
+	      }
+	    ]
+	  }
+	]
+      },
+      {
+        "@type" : "korap:token",
+        "wrap" : {
+          "@type" : "korap:term",
+          "foundry" : "tt",
+          "key" : "NN",
+          "layer" : "p",
+          "match" : "match:eq"
+        }
+      },
+      {
+	"@type" : "korap:group",
+	"class" : 2,
+	"operation" : "operation:class",
+	"operands" : [
+	  {
+	    "@type" : "korap:group",
+	    "operation" : "operation:repetition",
+	    "boundary": {
+	      "@type" : "korap:boundary",
+	      "min" : 2,
+	      "max" : 7
+	    },
+	    "operands" : [
+	      {
+		"@type" : "korap:token"
+	      }
+	    ]	     
+          }
+	]
+      }
+    ],
+    "operation" : "operation:sequence"
+  }
+}
diff --git a/src/test/resources/queries/sequence/empty-surround-repetition.jsonld b/src/test/resources/queries/sequence/empty-surround-repetition.jsonld
new file mode 100644
index 0000000..6b88e4f
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround-repetition.jsonld
@@ -0,0 +1,36 @@
+{
+   "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+   "query" : {
+      "@type" : "korap:group",
+      "operands" : [
+	 {
+             "@type" : "korap:token"
+         },
+         {
+            "@type" : "korap:token",
+            "wrap" : {
+               "@type" : "korap:term",
+               "foundry" : "tt",
+               "key" : "NN",
+               "layer" : "p",
+               "match" : "match:eq"
+            }
+         },
+	 {
+	 "@type" : "korap:group",
+	 "operation" : "operation:repetition",
+	 "boundary": {
+	   "@type" : "korap:boundary",
+	   "min" : 2,
+	   "max" : 7
+	 },
+	 "operands" : [
+	   {
+
+             "@type" : "korap:token"
+}]	     
+         }
+      ],
+      "operation" : "operation:sequence"
+   }
+}
\ No newline at end of file
diff --git a/src/test/resources/queries/sequence/empty-surround.jsonld b/src/test/resources/queries/sequence/empty-surround.jsonld
new file mode 100644
index 0000000..2e93da6
--- /dev/null
+++ b/src/test/resources/queries/sequence/empty-surround.jsonld
@@ -0,0 +1,25 @@
+{
+   "@context" : "http://ids-mannheim.de/ns/KorAP/json-ld/v0.1/context.jsonld",
+   "query" : {
+      "@type" : "korap:group",
+      "operands" : [
+	 {
+             "@type" : "korap:token"
+         },
+         {
+            "@type" : "korap:token",
+            "wrap" : {
+               "@type" : "korap:term",
+               "foundry" : "tt",
+               "key" : "NN",
+               "layer" : "p",
+               "match" : "match:eq"
+            }
+         },
+	 {
+             "@type" : "korap:token"
+         }
+      ],
+      "operation" : "operation:sequence"
+   }
+}
\ No newline at end of file